Quartz-halogen lamp and method of making



Dec. 1, 1970 J GEORGE ElAL 3,544,830

QUARTZ-HALOGEN LAMP AND METHOD OF MAKING Filed Oct. 25, 1968 FREDERICK J. GEORGE EDMUND R. KERN INVENTORS ATTORNEY United States Patent 3,544,830 QUARTZ-HALOGEN LAMP AND METHOD OF MAKING Frederick J. George, Hamilton, Mass., and Edmund R. Kern, Hampton, N.H., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Oct. 25, 1968, Ser. No. 770,569 Int. Cl. H01k 1/18, 3/06 US. Cl. 313-271 5 Claims ABSTRACT OF THE DISCLOSURE The legs of a U-shaped support wire are inserted into the coiled legs of a tungsten filament. The corners of the support wire are then welded to separate ribbon connectors and, after the filament assembly is mounted for press sealing, the crossbar of the U is severed. The ribbon connectors are then press sealed in a lamp envelope and the lamp is completed by exhausting, filling and sealing.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to single-ended quartz-halogen lamps. It particularly relates to a method of mounting and supporting a tungsten filament in such a lamp.

Description of the prior art Single-ended quartz-halogen lamps, such as are commonly used in film projectors, generally have a press seal at one end of a lamp envelope and a coiled tungsten filament disposed within the envelope. Generally the legs of the filament are connected to and supported by lead-in wires which, in turn, are connected to molybdenum ribbon connectors. The press seal generally embeds all of the ribbon connectors and a suflicient portion of the lead-in wires to structurally support them and the filament throughout the life of the lamp.

In the prior art, the lead-in wire usually consisted of a straight piece of tungsten wire, on end of which was connected to the filament leg and the other end of which was connected to the ribbon connector. The filament and lead-in wire assembly was often quite flimsy, especially where the lead-in wires were long in relation to the filament and where the filament wire was of small diameter. In those cases, it was diificult to mount the filament in the lamp envelope accurately since the filament could easily be distorted when the lead-in wires were welded to the ribbon connectors and the distortion could not be conveniently corrected at press sealing.

Distortion of the filament in a compact, high temperature lamp of the type involved herein can lead to premature failure of the lamps. In addition, distortion can result in an unsatisfactory positioning of the filament in relation to an associated reflector with a consequent inefiiciency of illumination of the projection screen.

It is an object of this invention to improve the process of assembling filaments in a single-ended quartz-halogen lamp.

SUMMARY OF THE INVENTION In accordance with this invention, a tungsten filament has coiled legs at both ends thereof, both legs protruding in about the same direction transverse to the axis of the filament body. Each leg of a supportwire, preferably U-shaped, is then inserted into each coiled leg of the filament for substantially the entire length of the coiled leg and is secured thereto. The configuration of the support wire is such as to engage the filament legs and support the filament body in an essentially relaxed state, that is,

3,544,830 Patented Dec. 1, 1970 without materially distorting the spacing of the body turns of the filament.

Ribbon connectors are then fastened, such as by welding, to each corner of the U-shaped support wire. (The junction of a leg of the U with the crossbar of the U is called a corner for the sake of convenience, even though it may be curved or may not have a sharp angle.) Each ribbon connector also has an external lead-in wire welded to it, the external lead-in wire protruding in a direction opposite to the legs of the U-shaped support wire.

The external lead-in wires are then clamped in a suitable device for the purpose of preventing relative movement of the filament legs and for supporting the filament assembly while it is being enclosed within a lamp envelope. The crossbar of the U is then severed, thereby terminating the direct physical connection of the molybdenum ribbons to each other. A lamp envelope is then disposed around the filament and press sealed at one end, as mentioned above, to embed the ribbons and structurally support the filament assembly. The clamping device is then removed and the lamp is completed by conventional methods of exhausting, filling and sealing.

' Preferably, the U-shaped support wire has a wire diameter that corresponds closely to the inside diameter of the coiled legs of the filament in order to provide a close fit upon insertion therein. Preferably, also, where the ends of the U-shaped support wire may be curved to permit miniaturization of the lamp envelope, the coiled legs have sufficient flexibility to accommodate the curved portions upon insertion thereon. Flexibility of the coiled legs can be increased by increasing the inside diameter of the coiling or by increasing the number of turns per inch thereof.

The purpose of inserting the support wire into sub stantially the entire coiled leg is to effectively short out the filament leg and thereby concentrate the lamp wattage in the filament body. Since the filament body is usually positioned at the focus of a curved reflector, the usable light is only that emitted by the body and lumen efliciency is correspondingly reduced when wattage is consumed in the filament legs.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is 'an elevational view of a single-ended lamp employing the support wire shown in FIG. 2, but showing the crossbar severed for proper lamp operation.

FIG. 2 shows an essentially U-shaped support wire inserted into the coiled legs of a tungsten filament in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A preformed support wire 1 as shown in FIG. 2 was made of 20 mil tungsten wire and was used in the manufacture of a 600 watt, volt, quartz-halogen lamp 2, shown in FIG. 1. Support wire 1 was substantially U-shaped, having legs 3 which were 0.610 inch long and crossbar 4 which was 0.235 inch long. The ends of legs 3 curved away from each other and then back into substantial parallel, so that the end 0.070 inch portions of legs 3 were spaced 0.445 inch apart from each other.

Filament 5 was made of 8 mil tungsten wire and was a coiled coil having a body length of 12.0 millimeters and a body diameter of 0.221 inch. Legs 6 of filament 5 were part of the primary coiling thereof, the primary coiling being Wound at 87.5 turns per inch on a 21 mil mandrel. Legs 6 were 9.0 millimeters long and both legs protruded in the same direction from filament 5. As shown in FIG. 2, legs 6 were bent toward each other to have a configuration corresponding to the ends of support wire 1. The reason for reducing the space between filament legs 6 below that of the body length of filament 5 was to permit lamp 2 to be as compact as practicable. Thus envelope 7, in which filament 5 was enclosed, was bulbous shaped, having a diameter of /4 inch at its central portion surrounding filament 5, but having a width of only /2 inch at its press seal.

Legs 3 of support wire 1 were then carefully inserted into coiled legs 6 of filament 5 for substantially the entire length of legs 6 without distorting the turn spacing of the body of filament 5. Legs 6 were then hot crimped on legs 3.

Molybdenum ribbon connectors 8, /8 inch wide by inch long, were then longitudinally welded, at one end thereof, to each corner of support Wire 1, the space between connectors 8 being inch. External lead-in wires, not shown, were then welded at the opposite ends of molybdenum ribbon connectors 8.

The external lead-in wires were then clamped in a holding device, not shown, and the portion of crossbar 4 between molybdenum ribbon connectors 8' was cut off. Quartz envelope 7, being open at its press seal end and having an exhaust tube at its other end, was then placed over the filament assembly so that the body of filament 5 was centrally positioned within the bulbous portion of envelope 7. The open end of envelope 7 was then press sealed on ribbon connectors 8 and the adjoining portions of support wire 1 and the external lead-in wires.

After removal from the holding device the lamp was exhausted, filled with a gas including halogen and sealed. The lamp was completed by operatively attaching ceramic base 9 having plug-in terminals to the press seal portion of the lamp.

We claim:

1. A quartz-halogen lamp comprising: a bulbous envelope having a press seal at one end thereof; two ribbon connectors embedded within said press seal; a coiled tungsten filament centrally disposed within said envelope, said filament having flexible coiled legs protruding toward said press seal; two support wires connected to separate ribbon connectors and inserted into substantially the entire length of separate coiled legs, the inserted portion of each support wire being partially curved and terminating in a short straight end and the portion of each support wire connected to each ribbon connector being corner shaped; and separate external lead-in wires connected to each ribbon connector.

2. The lamp of claim 1 wherein the ends of said coiled legs are substantially parallel to each other and spaced apart a lesser distance than the body length of said filament.

3. The lamp of claim 2 wherein the width of said press seal is less than the diameter of the bulbous portion of said envelope.

4. In a method of manufacturing a single-ended quartzhalogen lamp, the steps which comprise: forming a tungsten filament having an elongated coiled body and coiled legs at the ends thereof, said legs protruding in the same direction substantially transverse to said body; inserting the ends of a single support wire into said coiled legs; securing said coiled legs to said support wire; connecting two spaced apart ribbon connectors to separate corners of said support wire; connecting external lead-in wires to said ribbon connectors; supporting said external lead-in wires in a clamping device; severing a portion of said support wire between said ribbon connectors; centrally positioning said filament in a bulbous envelope open at one end; press sealing the open end of said envelope to said ribbon connectors; removing said clamping device; and exhausting, filling and sealing said envelope.

5. The method of claim 4 wherein said support wire is U-shaped and said ribbon connectors are each connected to a corner thereof.

References Cited UNITED STATES PATENTS RAYMOND F. HOSSFELD, Primary Examiner US. Cl. X.R. 

